1. Field of the Invention
This invention relates to a suspension system for vehicle in the form of a shock absorber loaded therearound with a compression coil spring and more particularly to such suspension system for a vehicle adapted to alleviate a force generated by the compression coil spring and directed perpendicularly to a coil axis (referred to hereinafter as "side forces").
2. Description of the Prior Art
Recently, high strength spring steel has been put to practical use and various improved working techniques such as special shot peening in order to obtain a light weight and compact product. Such efforts have increased design stress as well as pitch angle of a suspension coil spring. However, such improvement has often been accompanied with an apprehension that, even when the spring seat is displaced only in the coil axis (so-called parallel compression), a side force might be generated. Particularly when the shock absorber is loaded with such compression coil spring, such side force may often cause an absorber rod and an absorber tube to be jammed together and eventually may result not only in uncomfortable drive conditions, but also premature deterioration of the shock absorber.
To avoid such problems, various efforts have been made to alleviate the side force, for example, upper and/or lower sheets have been inclined or offcentered on the basis of a value obtained from various experiments or analytical research according to the finite element method.